Wheel-to-surface contact patch force variation

Abstract

A control system ( 300 ) for controlling an active suspension system ( 104 ) of a vehicle ( 100 ), the active suspension system comprising suspension actuators ( 502 ), the control system comprising one or more controller ( 301 ), wherein the control system is configured to: in dependence on an activation signal ( 904 ), provide ( 908 ) a control signal to the active suspension system to cause the suspension actuators of the active suspension system to repetitively pulse vertical force through wheels (FR, FL, RR, RL) of the vehicle in a controlled pattern determined by the one or more controller, to vary wheel-to-surface contact patch forces, wherein the pattern comprises repetitively pulsing vertical force through at least one of the wheels at a first phase and through at least one other of the wheels at a second phase.

The invention claimed is: 
     
       1. A control system for controlling an active suspension system of a vehicle, the active suspension system comprising suspension actuators, the control system comprising at least one controller, wherein the control system is configured to:
 in dependence on an activation signal, provide a control signal to the active suspension system to cause the suspension actuators of the active suspension system to repetitively pulse vertical force through wheels of the vehicle in a controlled pattern determined by the at least one controller, to vary wheel-to-surface contact patch forces, 
 wherein the pattern comprises repetitively pulsing vertical force through at least one of the wheels at a first phase and through at least one other of the wheels at a second phase. 
 
     
     
       2. The control system of  claim 1 , wherein the control system is configured to receive surface information, and in dependence on the surface information:
 enable the control signal to be provided to the active suspension system; and 
 determine the pattern; and/or 
 determine one or more pulsation characteristics of the pattern. 
 
     
     
       3. The control system of  claim 2 , wherein the surface information is dependent on one or more of: a selected terrain mode of the vehicle, and information obtained from one or more sensors. 
     
     
       4. The control system of  claim 1 , wherein the pattern is configured to:
 pulse a first set of the suspension actuators at first diagonally-opposite corners of the vehicle at the first phase, and 
 pulse a second set of the suspension actuators at second diagonally-opposite corners of the vehicle at the second phase. 
 
     
     
       5. The control system of  claim 1 , wherein the second phase is approximately 180 degrees offset from the first phase. 
     
     
       6. The control system of  claim 1 , wherein
 the at least one wheel is a first wheel; 
 the first wheel is at a first lateral side of the vehicle and at a first longitudinal end of the vehicle; 
 the at least one other wheel is a second wheel; 
 the second wheel is at a second lateral side of the vehicle and at the first longitudinal end of the vehicle; and 
 the pattern is configured to:
 pulse a suspension actuator of the first wheel at the first phase, 
 pulse a suspension actuator of the second wheel at the second phase, 
 pulse a suspension actuator of a third wheel at a third phase, wherein the third wheel is at the second lateral side and at a second longitudinal end of the vehicle; and 
 pulse a suspension actuator of a fourth wheel at a fourth phase, wherein the fourth wheel is at the first lateral side and at the second longitudinal end. 
 
 
     
     
       7. The control system of  claim 1 , wherein the repetitive pulsing for a given suspension actuator comprises
 pulsing the vertical force at one or more controlled frequencies determined by the at least one controller; or 
 pulsing the vertical force at a plurality of frequencies concurrently. 
 
     
     
       8. The control system of  claim 7 , wherein the one or more frequencies comprise a frequency having a value within a range from approximately 0.25 Hz to approximately 3 Hz. 
     
     
       9. The control system of  claim 7 , wherein the one or more frequencies comprise a frequency having a value within a range from approximately 8 Hz to approximately 15 Hz. 
     
     
       10. The control system of  claim 1 , wherein the control system is configured to change at least one of a pulsation amplitude and a pulsation frequency in dependence on information from one or more tire pressure monitors associated with the wheels of the vehicle. 
     
     
       11. The control system of  claim 1 , wherein
 a pulsation characteristic for one of the suspension actuators is different from the pulsation characteristic for another of the suspension actuators; and 
 the pulsation characteristic is at least one of a pulsation amplitude and a pulsation frequency. 
 
     
     
       12. The control system of  claim 11 , wherein
 the pulsation frequency is different in dependence on a suspension natural frequency associated with the one of the suspension actuators being different from the suspension natural frequency of the another of the suspension actuators, or 
 the pulsation amplitude is different in dependence on information from tire pressure monitors associated with the wheels of the vehicle associated with the one of the suspension actuators and the another of the suspension actuators, respectively. 
 
     
     
       13. The control system of  claim 1 , wherein the control system is configured to change a pulsation characteristic of the pattern in dependence on one or more sensed variables associated with vehicle movement. 
     
     
       14. The control system of  claim 13 , wherein the pulsation characteristic is changed to inhibit low frequency pulsation, in dependence on at least one of the sensed variables falling below a threshold. 
     
     
       15. The control system of  claim 14 , wherein the pulsation characteristic is changed to increase a pulsation amplitude in dependence on at least one of the sensed variables falling below a threshold. 
     
     
       16. The control system of  claim 14 , wherein the at least one sensed variable comprises at least one of vehicle speed and wheel speed. 
     
     
       17. The control system of  claim 14 , wherein
 changing the pulsation characteristic is a nonbinary change; or 
 the pattern is a pre-stored pattern that is stored in a memory. 
 
     
     
       18. A vehicle comprising the control system of  claim 1 . 
     
     
       19. A method of controlling an active suspension system of a vehicle, the active suspension system comprising suspension actuators, the method comprising:
 in dependence on an activation signal, providing a control signal to the active suspension system to cause the suspension actuators of the active suspension system to repetitively pulse vertical force through wheels of the vehicle in a controlled pattern determined by at least one controller, to vary wheel-to-surface contact patch forces, 
 wherein the pattern comprises repetitively pulsing vertical force through at least one of the wheels at a first phase and through at least one other of the wheels at a second phase. 
 
     
     
       20. A non-transitory storage medium containing instructions that, when executed by at least one processor, cause the processor to perform the method of  claim 19 .